The Night Sky This Month: January 2016

The moon always offers something to see, and on the night of January 18th, two of the greatest craters on the moon, Tycho, and Copernicus are especially well placed for binocular observers. At just over one hundred million years old, 85 km in diameter, and 5 km deep, Tycho is thought to have been created by a remnant of the body that broke up to create the asteroid Baptistina. Also interesting is the distinct possibility that another remnant of the same break-up caused the extinction of the dinosaurs, after the Chicxulub impact about 65 million years ago.

Copernicus is located in the eastern reaches of the Oceanus Procellarum, just beyond the termination of the Apennine Mountains. Estimated to be about eight hundred million years old, Copernicus is a classic terraced crater 93 km in diameter, and about 4 km deep.

Moon Phases

Last Quarter: January 2nd
New Moon: January 10th
First Quarter: January 16th
Full Moon: January 24th

Comet Catalina

January sees the Comet Catalina moving into the northern skies, and at the beginning of the month it might just be bright enough to observe without optical aid a little above the star Arcturus in Bootes. Observers with acute vision may be able to track the comet unaided, but the use of a small telescope or binoculars is recommended for the best views. During the month, Catalina will move almost due north until it moves through the handle of the Big Dipper in Ursa Major by month’s end.

The Planets

The month of January does not offer anything especially spectacular as far as the planets go, but the clear winter air should make for good viewing conditions to see whatever there is to see, weather permitting of course.

Mercury

New Year’s Day sees Mercury shining at magnitude -0.4, roughly 7 degrees above the horizon in the south-west half an hour after sunset. However, it will only be visible with binoculars, so do not try to spot is before the sun has fully set. Over the first week of the month, it will be progressively lower in the sky, and its magnitude will decrease to around +1.8, making it increasingly difficult to find. On the 14th of the month, Mercury will then pass though an inferior conjunction with the sun, so with some luck, it might just be visible in the east just before dawn, its magnitude being 0.0 toward the end of the month.

Venus

At the beginning of the month, Venus will rise about three hours before dawn, decreasing to about two hours by the month’s end. In the first few days of the month, Venus will only be 1 degree from Beta Scorpii, before it moves into Sagittarius, passing close to M20 (Trifid Nebula), before reaching the handle of the Teapot asterism by the beginning of February. During January, Venus’ angular diameter will decrease from 14.3 to 12.4 seconds of arc, but since its illumination will increase from 77% to 85%, its magnitude will remain almost unchanged during the whole of the month.

Mars

Starting the month about 6 degrees from the star Spica, Mars will move eastwards with respect to the background stars, reaching the constellation Libra by the middle of the month. Mars’ magnitude will increase from +1.3 to +0.8 as it angular diameter increases to 5.6 to 6.8 seconds of arc, which means that with exceptionally good seeing conditions it might be possible to discern the polar ice caps and perhaps features like Syrtis Major. However, Mars will be at opposition in May, when these details might be easier to spot, it’s disc being three times larger then. Mars will end the month being just 1.3 degrees north of the binary system Alpha Librae.

Jupiter

Rising at about 20:30 UT, Jupiter starts the month in the south-eastern reaches of the constellation Leo, shining at magnitude -2.2. Jupiter is also starting its retrograde motion, moving westwards, and by month’s end, it will have culminated at an elevation of 45 degrees over the southern horizon at about 01:30 UT. Earth is now approaching Jupiter, and as it does, Jupiter will increase in size from 39, to 42.4 seconds of arc, so early risers should see the equatorial bands, and even the Great Red Spot, seeing conditions permitting.

Saturn

Saturn is now a morning object, rising at about 06:15 UT, and it starts the month about 7 degrees to the upper-leftward of the star Antares in the southern reaches of the constellation Ophiuchus, shining at magnitude +0.5. As the month wears on, Saturn’s diameter will increase from 15.3, to 15.8 seconds of arc, but the ring system will span a full 35 arc seconds. Look for Saturn in the south-east before dawn- the ring system is now inclined at about 25 degrees, and it is always a spectacular sight even in modest telescopes.

Deep Sky Objects

Pleiades Cluster (M45)

The constellation Taurus offers many spectacular sights, but there are none as beautiful as the Pleiades Cluster (M45). Consisting of more than 3,000 stars spanning 13 light years, the cluster shines with an eerie blue light as it moves through a section of an enormous molecular cloud on its way towards the star Betelgeuse in Orion. The blue haze that permeates the Pleiades is caused by the reflection of star light from the abundant small grains of carbon in the molecular cloud. However, the blue haze is the result of the cluster’s passing through the cloud 4,00 years ago, and the blue reflection we see is only reaching us now.

The Constellation Orion

Orion is perhaps the most easily recognized of all the constellations, and in the northern skies, it is now best seen at around midnight. Orion contains many major stars, with Betelgeuse (Alpha Orionis), varying in size from around 300 times to close to 400 times the size of the sun. However, the two most striking features of Orion are the Horse Head Nebula, and the Orion Nebula in the hunter’s “sword”.

The Horse Head Nebula

This nebula that resembles a knight on a chess board is a pillar of dust and gas seen against the background of a larger area of nebulosity, and although is it exceedingly difficult to observe visually even with large instruments, it makes an excellent target for astrophotography. Many amateur astro-photographers have used the Horse Head Nebula to hone their skills, and today, many images by amateur photographers rival those taken by professional astronomers using state-of-the-art equipment.

Orion Nebula

The other noteworthy object in Orion is the nebula that “hangs off” the central star in the sword. In good seeing conditions, and with a color corrected telescope, it is possible to discern the glow in the nebula that results from the light emitted by the ionized oxygen in the nebula. The ionization of the oxygen in the nebula is mostly done by the four powerful stars that make up the Trapezium asterism; however, even though images show the glow as red, human vision is much more sensitive to the green component of the emitted light, so if you look at the nebula long enough, you may see it as green, and not red.

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